Despite all the media attention given to oil shale and oil from shale, or “tight oil,” there exists a great deal of confusion about the two.
Oil shale is a petroleum precursor that requires cooking to get the oil and natural gas out (e.g. Green River oil shale deposits in the Western United States).
Tight oil is crude oil stored in shale and requires modern drilling and recovery techniques to get it out (e.g. Bakken and Niobrara shale deposits). Natural gas is also produced from shale deposits.
What are the origins of these two different kinds of oil?
Millions of years ago algae and plankton died and sank to the bottom of lakes and seas. As they lay on the bottom of the sea or lake, they were buried under layers of mud and sand. Over millions of years more and more mud and sand covered them. The layers of mud and sand pushed the dead stuff further into the ground, squashing it under higher pressures and temperatures.
This heat and pressure squashed the layers of mud together turning it into a special kind of rock called shale, just as the sand was compressed to make sandstone. The heat and pressure also turned the dead stuff, squashed inside the shale rock, into oil’s beginnings – kerogen.
There are some areas where the heat and pressure continued to ‘cook’ the kerogen converting it into crude oil. Some oil migrated into traditional oil reservoirs. The oil that remained in the shale is known as “tight oil.”
There are also areas where the kerogen trapped inside the shale did not get hot enough to ‘cook’ and was not yet crude oil. This is called “oil shale”. It is possible to extract crude oil from oil shale, by finishing off Mother Nature’s work by ‘cooking’ the rock faster.
The crude oil obtained from both sources can be made into high quality products such as gasoline, jet fuel and diesel to fuel our cars, trucks and planes.
Submitted by Roger Day, chairman, and Glenn Vawter, executive director, National Oil Shale Association P.O. Box 3080,
Glenwood Springs, CO 81601 970-389-0879, 970-945-423(Fax) email@example.com